/*
 * Copyright (C) 2005 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * DEPRECATED.  DO NOT USE FOR NEW CODE.
 */

#ifndef ANDROID_SHARED_BUFFER_H
#define ANDROID_SHARED_BUFFER_H

#include <stdint.h>
#include <sys/types.h>
#include <atomic>

// ---------------------------------------------------------------------------

namespace android {

    class SharedBuffer {
    public:

        /* flags to use with release() */
        enum {
            eKeepStorage = 0x00000001
        };

        /*! allocate a buffer of size 'size' and acquire() it.
         *  call release() to free it.
         */
        static SharedBuffer *alloc(size_t size);

        /*! free the memory associated with the SharedBuffer.
         * Fails if there are any users associated with this SharedBuffer.
         * In other words, the buffer must have been release by all its
         * users.
         */
        static void dealloc(const SharedBuffer *released);

        //! access the data for read
        inline const void *data() const;

        //! access the data for read/write
        inline void *data();

        //! get size of the buffer
        inline size_t size() const;

        //! get back a SharedBuffer object from its data
        static inline SharedBuffer *bufferFromData(void *data);

        //! get back a SharedBuffer object from its data
        static inline const SharedBuffer *bufferFromData(const void *data);

        //! get the size of a SharedBuffer object from its data
        static inline size_t sizeFromData(const void *data);

        //! edit the buffer (get a writtable, or non-const, version of it)
        SharedBuffer *edit() const;

        //! edit the buffer, resizing if needed
        SharedBuffer *editResize(size_t size) const;

        //! like edit() but fails if a copy is required
        SharedBuffer *attemptEdit() const;

        //! resize and edit the buffer, loose it's content.
        SharedBuffer *reset(size_t size) const;

        //! acquire/release a reference on this buffer
        void acquire() const;

        /*! release a reference on this buffer, with the option of not
         * freeing the memory associated with it if it was the last reference
         * returns the previous reference count
         */
        int32_t release(uint32_t flags = 0) const;

        //! returns wether or not we're the only owner
        inline bool onlyOwner() const;


    private:
        inline SharedBuffer() {}

        inline ~SharedBuffer() {}

        SharedBuffer(const SharedBuffer &);

        SharedBuffer &operator=(const SharedBuffer &);

        // Must be sized to preserve correct alignment.
        mutable std::atomic<int32_t> mRefs;
        size_t mSize;
        uint32_t mReserved[2];
    };

    static_assert(sizeof(SharedBuffer) % 8 == 0
                  && (sizeof(size_t) > 4 || sizeof(SharedBuffer) == 16),
                  "SharedBuffer has unexpected size");

// ---------------------------------------------------------------------------

    const void *SharedBuffer::data() const {
        return this + 1;
    }

    void *SharedBuffer::data() {
        return this + 1;
    }

    size_t SharedBuffer::size() const {
        return mSize;
    }

    SharedBuffer *SharedBuffer::bufferFromData(void *data) {
        return data ? static_cast<SharedBuffer *>(data) - 1 : 0;
    }

    const SharedBuffer *SharedBuffer::bufferFromData(const void *data) {
        return data ? static_cast<const SharedBuffer *>(data) - 1 : 0;
    }

    size_t SharedBuffer::sizeFromData(const void *data) {
        return data ? bufferFromData(data)->mSize : 0;
    }

    bool SharedBuffer::onlyOwner() const {
        return (mRefs.load(std::memory_order_acquire) == 1);
    }

}; // namespace android

// ---------------------------------------------------------------------------

#endif // ANDROID_VECTOR_H
